1. WASHING & DRYING PROCESSES FOR RECYCLED PLASTICS Problem Statement: To determine a method of cleaning and drying a continuous stream of shredded high density polyethylene before it proceeds to granulation in the recycling line of Louis Padnos Iron & Metal Company. The process should involve removing all foreign materials, some of which may need to be collected for alternate processing. Economic Analysis: Student Design Team: Seunghee Han Richard Pospiech Matthew Siero William Smits Project Sponsor: Louis Padnos Iron & Metal Company Holland, MI Sponsor Representatives: Mr. Bob Herweyer Mr. Martin Przekadzinski Faculty Advisor Dr. Indrek Wichman Layout #1 Layout #2 Initial Cost ($)750,000 Throughput (lbs/hr) 3,0005,000 Annual Operating Cost ($/year) 14,66418,24233,05138,064 Price (¢/lb)4.724.883.343.47 Initial Cost ($)1,500,000 Throughput (lbs/hr) 3,0005,000 Annual Operating Cost ($/year) 16,12021,13334,50740,955 Price (¢/lb)8.839.065.805.98 Analysis: Layout #1 This layout is expected to clean light contaminants, including dirt and light syrups. The estimated cost is $750,000 Layout #2 This layout is expected to clean heavy contaminants, including dirt, labels, and heavy syrups. The estimated cost is $1,500,000 Layout Throughput (lbs/hr) Unit Cost ( ¢ /lb) 1 30000.292 50000.366 2 30000.339 50000.394 Table 3. The cost analysis for Layout #1 Methods: Table 1. Operating cost per pound of plastic Table 1 shows the operating cost of running each layout with two different throughputs. The cost is shown as a unit price per pound of plastic for a cold wash system, assuming 8 hour work days. Figure 3. Initial heating costs per 10 m 3 of water Table 2. The cost of running a hot water wash system If the contaminants include adhesives and stickers, a hot water wash will be necessary to clean the plastic. Figure 3 shows the cost of heating 10 m 3 of water from 10° C to various temperatures. The blue line shows the cost using an electric heater, while the pink line shows the costs of heating with a gas heater. Table 2 shows the cost per pound of plastic if a hot water wash system is used. The prices are shown for two different heater types and throughputs. Table 4. The cost analysis for Layout #2 Conclusion: Tables 3 and 4 show the necessary selling price in order to justify the costs of the system after 20 years for each system with a throughput of 3,000 and 5,000 lbs/hr. This analysis is for cold wash systems only. Due to the uncertainty of possible contaminants, two final processes are recommended to clean and dry the HDPE shred. Layout #1 can remove all contaminants effectively, except heavy syrup, stickers, and adhesives. Layout #2 will be suitable for removing tougher contaminants, such as thick syrups and labels. For a system capable of removing stickers and adhesives, a warm water wash must be used; however, will be expensive to operate and is not recommended. Both Layouts are capable of a throughput of 3,000 lbs/hr and 5,000 lbs/hr, depending on the specific machinery selected. From the above procedure, the following four methods were determined to be the best for each process The following flowchart illustrates the procedure used for designing the plastic washing and drying line. Friction Washer Problem Statement Design Parameters Researching Equipment Decision Matrix Initial Layouts Vendor Interviews Final Process Layouts Operating Cost Analysis Hot Wash Analysis Economic Analysis Final Recommendation Metal Removal Density Separation Washing Drying Magnet Electromagnet Electrostatic Drum Eddy-Current Sink-Float Tank Hydrocyclone Centrifugal Drying Friction Washer Air Cleaning Thermal Drying Centrifugal Washing Water Jet Washer Steam Washing Sink/Float Tank Centrifugal Washer/Dryer Thermal Dryer Operating Temperature of Water (°C) 3,000 lb/hr Throughput5,000 lb/hr Throughput Cost ($/lb) - Electric Heater Cost ($/lb) - Gas Heater Cost ($/lb) - Electric Heater Cost ($/lb) - Gas Heater 22< 0.01 320.030.010.020.01 420.050.020.030.01 520.070.04 0.02 620.090.050.060.03 720.110.060.070.03 820.140.070.080.04 920.160.080.090.05